Radar antenna



Sept. 22, 1953 o. E. SZEKELY 2,653,240

RADAR ANTENNA Filed April 27, 1951 4 Sheet5-Sheet l INVENTOR.

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0. E. SZEKELY Sept. 22, 1953 RADAR ANTENNA 4Sheets-Sheet 2 Filed April 27 1951 INVE/NTOR. OTTO E; SZEKELV ATTORNE s.

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RADAR ANTENNA Filed April 27, 1951 4 Sheets-Sheet 4 OTTO E. SZEKELV FIG. 5 BY ATTORNEYS.

Patented Sept. 22, 1953 RADAR ANTENNA Otto E. Sz'ekely, Philadelphia, Pa., assignor to 0. E. Szekely & Associates, Inc., Philadelphia, Pa., a corporation of Pennsylvania Application April 27, 1951, SerialNo. 223,216

'5 Claims. 1 This invention relates to an improved radar antenna for use in aircraft.

Radar antenna for use in aircraft must be capable of scanning the terrain in front of the rays. The returning rays which impinge on the reflector are carried to a screen and thus present a picture of the objects from which the rays have been reflected.

In order that the maximum area may be covered, the spindle and the wave guide, the Cutler feed and the reflector are driven by a mechanism which causes them to rotate and to have azimuth angular deflection. Azimuth angular deflection is frequently called nod or scan. The spindle may rotate and nod at the same time. When this occurs, the wave guide, the Cutler feed and the reflector move through a spiral configuration. Thus they scan a cone of volume directly forward of the airplane. This motion is continuous and rapid since the spindle, wave guide and reflector rotate at speeds up to 1200 R. P. M.

The power required to drive a mechanism which is rotating rapidly and changing the "angular position of the center of rotation at the same time, is greater than that required to merely rotate the mechanism when rotating about a fixed center. This is due to the power required to change the angular position of the center line of rotation of a rotating mass. The gyroscope operates on this principle The reflector, which is dish-shaped, causes considerable friction with the air when driven at high rotating speeds and rapid angular deflections. Also, when a fixed reflector is rotating and spiraling at high speed, the reflector is distorted due to centrifugal and air friction forces. i-ience, the parabolic surface of the reflector is no longer a true parabola and the pictures are blurred. Further, the parabolic surface of the reflector is not perfect even when at rest. Hence, when the reflector is rapidly rotating, successive rays which may impinge on the reflector at rates up to 4000 I pulses per second, are reflected from imperfections in the reflector. These rays successively reflected from imperfections in the reflector, cause the picture to be blurred.

Reduction of weight and size is of utmost importanee in all airborne equipment. A reduction in the power required to drive a radar antenna results in a reduction in the "weight and cost of the driving mechanism. Therefore, is evident that any reduction in the power required will result in substantial savings in cost, weight and size of the mechanism since all items such as generators, motors and mechanical mechanisms are reduced in proportion to the decreased power requirement.

It is, therefore, a primary object of this invention to provide an improved radar antenna in which the reflector is freely mounted for rotation independently of the spindle.

It is a further object of this invention to provide an improved radar antenna, including a freely rotatable reflector, which requires less power to drive the mechanism due to the reduced gyroscopic mass of the reflector and the reduced wind resistance of the reflector due to rotation.

It is a further object of this invention to provide an improved radar antenna, including a freely rotatable reflector, of reduced size and weight and yet with capacity to drive much larger reflectors than has been considered .possible previously.

It is a further object of this invention to provide an improved radar antenna, including a freely rotatable reflector, in which an improved picture is obtained due to the fact that since the free reflector remains substantially stationary when the Cutler feed is rotating the rays from the Cutler feed and the returning rays from the target impinge on different points on the parabolic reflector surface thus preventing distortion of successive rays.

It is a further object of this invention to pro vide an improved radar antenna, including a freely rotatable reflector, in which distortion of the reflector, due to centrifugal forces, is considerably reduced.

It is a further object of this invention to provide an improved radar antenna, including a freely rotatable reflector, which, when used with a reversible motor, permits the use of a smaller motor than would otherwise be necessary, due to the fact that when the motor is reversed, the necessity of overcoming the inertia of the rotation of the reflector about its axis is eliminated.

These and other objects of this invention will become apparent from a consideration of the accompanying drawings in which one embodiment of this invention is disclosed.

Figure 1 is a schematic perspective view partly 3. broken away of an improved radar antenna incorporating this invention.

Figure 2 is a side view partly broken away of an improved antenna incorporating this invention.

Figure 3 is a top view partly broken away of an improved radar antenna incorporating this invention.

Figure 4 is an enlarged view taken on line 4-4 of Figure 3, showing the shifting mecha nism employed in the device of this invention for shifting from wide to narrow scan.

Figure 5 is a sectional view of the shifting mechanism shown in Figure 4, taken on line 5-5 of Figure 4.

Referring specifically to Figure 1, a main drive motor 2 is mounted on a main housing, not shown, which is affixed to an aircraft. Main drive motor 2 Wound motor of the reversible type. Main drive motor 2 has shaft 2 mounted therein having ear 6 mounted thereon. Gear 6 meshes with gear 8 which is afiixed to cross-shaft I6. Crossshaft It has a worm gear I2 mounted thereon. Clutch It, actuated by a solenoid, not shown, is. also mounted on cross-shaft ID, adjacent worm gear I2. Worm gear teeth It are cut on crossshaft I6 near the right-hand end thereof as viewed in Figure 1 and engage with gear 58. Gear I3 is mounted on the top of shaft 22. Worm gear teeth 22 are cut on the center of shaft 25} and engage with gear 24 mounted on shaft 23. Shaft 26 has position button contact switch 28 mounted on the right-hand end thereof and engages a crank arm 36 at the left-hand end thereof, as viewed in Figure 1.

As best seen in Figure 5, crank arm 36 has a stud 32 projecting therefrom upon which is rotatably mounted connecting rod 3t.

Connecting rod 3% engages a shifting fork which, in turn engages shifting collar 36 which is rotatably mounted on spindle 38. Spindle 38 is rotatably mounted in supporting bracket td as by ball bearings 42. Mounted on the left-hand end of spindle 38 is supporting bracket fi i in which is journalled azimuth pinion 26 on ball bearings 46 and 56, as shown in FigureZ.

As best seen in Figure 2, azimuth pinion 25 has wave guide 52 mixed thereto as shown at 55. Wave guide 52 has a Cutler type primary feed 55 mounted at the end thereof and dipole 56 mounted. thereon.

As best seen in Figures 2 and 3, weight frame 58 is fixedly secured to azimuth pinion ie at the top thereof as shown at 60. Weight frame 56 is rotatably secured to supporting bracket M at the bottom thereof, as viewed in Figure 2, being mounted on bearings 62.

As best seen in Figure 3, weight frame 58 has ears (i l and SE protruding from the front thereof. Ears 64 and t6 have two oppositely disposed holes therein having bearing sleeves 68 and 12 therein in which are mounted headed bolts E2 and it. Headed bolts 12 and M are threaded into supporting bracket l6, upon which is freely mounted reflector supporting plate I8 by bearings 3%. Supporting plate 78 has perforated parabolic reflector 82 mounted thereon.

As best seen in Figures 1, 2 and 3, azimuth pinion do has a sleeve 84 thereon having gear teeth 36 cut therein. Gear teeth 86 mesh with corresponding teeth on rack 88, said rack being secured to rod 69 which is attached to shifting collar pindle 36 is journalled in housing 92 on bearings 42 and 94.. Hollow spindle 36 has is a direct current, compound.

V a passageway 96 therein for the passage of electronic impulses. The electronic impulses pass through wave guide 52 through passageway 98 in azimuth pinion 46, through elbow I 60, through passageway 96 in hollow spindle 3S and passageway IllI in member I62, abutting the right-hand end of spindle 38, as viewed in Figure 3, Where they are received and displayed on a cathode ray oscillograph. It will be appreciated by those skilled in the art that transmitted as well as received impulses pass through this same channel.

Engaging shifting collar 36 at its upper end and being rotatably pinned at its lower end to housing 92 is a shifting fork Hi l which has one end of connecting rod 34 attached thereto, as shown at I66. Mounted adjacent shifting fork His is spindle drive gear I65 which meshes with Worm gear I2 on cross-shaft m. Spindle drive gear I65 may be affixed to spindle 33 by any convenient means. Mounted below spindle drive gear I65, as viewed in Figure 2, is indexing solenoid I 62, the purpose of which is to index the spindle when the spindle is not rotating so that dipole 56 is in the proper position. Mounted above the right-hand end of spindle 36, as viewed in Figure 2, is tilt motor iIIl which is actuated by tilt potentiometer I I 1, shown in Figure 3. Tilt motor I I 6 actuates a shifting fork which, in turn, actuates shifting collar M2 to which is attached rod H2. Rod H4, at its left-hand end, as viewed in Figure 2, attaches to a yoke, not shown, which tilts the perforated paraboloid reflector and supporting plate I8 when the spindle 36 is not rotating.

Mounted on the end of shaft 26, as viewed in Figure 3, is a speed control unit housing I I6 having switch 28 therein.

Referring specifically to Figures 4 and 5, it will be seen that shaft 26 is journalled in bearings lII6. Shaft 26 has a, circular plate E29 formed integral with the end thereof, upon which is mounted gear 24. by pin I22. Gear 24 has a hole 23 therein for the reception of stud I2 3, having nut I25 thereon, which in integral with plate I26. Plate I26 has an opening therein for the reception of pilot I28 formed integral with shaft 26. Also mounted on pilot I 28 and being secured to plate I26 by a pin E36 is circular plate I32 which is mounted oii center with respect to shaft 26. Secured to plate I32, as by screws I34, is face plate I 36. Face plate I36 has a U-shaped slot I38 therein. Slidably mounted between plates I32 and I36 is member I46 having stud 3 integrally formed therewith. Stud 32 has a shoulder I42 formed thereon. Mounted between shoulder M2 and nut MM is connecting rod 34 which is attached toshifting fork H3 at its other end, as previously described.

It will be seen from Figures 4 and 5 that when the stud 32 is in the position shown in Figures 4 and 5, and the device is operated, that the antenna will then scan a wide area due to the length of the crank arm which is the distance from the center of rotation of shaft 26 to the position of stud 32 in slot I38. In order to operate the antenna on narrow scan, the drive motor is reversed thus changing the direction of rotation of shaft 26 and causing stud 32 to move to the opposite end of slot I36 from that shown in Figure 4. In this position, it will be seen that the length of the crank arm from the center of rotatlon of shaft 26 to stud 32 is much smaller than the length of the crank arm when the device is operated as shown in Figure 4. This results from the eccentric mounting of plates I32 and I36 on shaft 28.

The operation of the device is as follows:

When main drive motor 2 is energized, it drives shaft 4, gear 6, gear 8 and cross-shaft I0, having worm gear I2 mounted thereon. Worm gear I2 meshes with main drive gear I05 which is aflixed to spindle 38 and thus spindle 38 is rotated. Spindle 38, in its rotation, rotates azimuth pinion 46, having weight frame 58 aflixed thereto, and also rotates wave guide 52. It will be appreciated that due to the free mounting of parabolic reflector 82, it will either not rotate at all or it will rotate at a slower speed with respect to spindle 38 and wave guide 52, due to the friction in bearings 80.

The rotation of cross-shaft II] also rotates gear I8 by virtue of worm gear teeth I6 meshing therewith. Gear I8 rotates shaft 20, having teeth 22 thereon, which mesh with gear 24 aflixed to shaft 26. As shaft 26 rotates, stud 32, having connecting rod 34 mounted thereon, is also rotated. The reciprocating motion of connecting rod 34 oscillates shifting collar 36, having rod 90 affixed thereto. Rod 90 has a rack 88 mounted on the end thereof meshing with gear teeth 86 on sleeve 84. Since sleeve 84 is firmly afiixed to azimuth pinion 46, wave guide 52 is driven through a predetermined azimuth angular deflection or nod. Thus it is seen that when the device is operated, the rotation of spindle 38 and the nod of the wave guide 52 causes the wave guide, Cutler feed and reflector to move through aspiral configuration. Thus they scan a cone of volume directly forward of the airplane.

When it is desired to shift from wide to narrow scan, main drive motor 2 is reversed, thus causing a reversal of the drive to spindle 38. When this occurs, stud 32 shifts to the opposite end of slot I38 thus shortening the length of the crank arm on the end of shaft 26. This shortens the period of oscillation of sleeve 38 and consequently that of rack 88. Thus the azimuth angular deflection of wave guide 52 will be reduced. It will be appreciated that When the direction of rotation of spindle 38 is reversed, there will be considerable inertia in parabolic reflector 82 due to the rotation thereof, caused by the friction in bearings 80. However, due to the fact that reflector 82 is freely mounted on bracket I6, attached to Weight frame 58, it will be unnecessary to overcome this inertia in reversing the direction of rotation. Reflector 82 will continue to rotate until the friction in bearings 80 is sufficient to cause it to reverse its direction of rotation.

Fromthe foregoing, it will be appreciated that due to the fact that it is unnecessary to overcome the inertia of reflector 82 in reversing the direction of rotation of spindle 38, the size of the motor and mechanical mechanisms can be reduced in proportion to the decreased power necessary to change the direction of rotation. It will also be appreciated that due to the fact that the freely mounted reflector does not rotate at as high a speed as the spindle, that air friction is reduced, and also that the wind resistance and the gyroscopic mass due to the rotation will both be reduced. Further, the decreased speed of rotation of the reflector results in less distortion, due to the decreased centrifugal and air friction forces. Hence, the free reflector will maintain a more perfect parabolic surface than a fixed reflector and thus produce a more perfect picture. n ther, due to the fact that the reflector is freely mounted, it will be seen that the relative position of the Cutler feed and the reflector is continuously changing and imperfections in the parabolic surface of the reflector will not reflect successive rays which form a given part of the picture. Since these rays impinge at rates up to 4000 pulses per second, a few distorted rays among the perfect rays will not blur the picture. Hence, the free reflector, even though it may have as many imperfections in its parabolic surface as the fixed reflector, will produce a more perfect picture.

It will be appreciated by those skilled in the art that various modifications may be made within the scope of this invention without departing from the pirit thereof, and the scope of the invention is to be restricted only in accordance with the appended claims.

What is claimed is:

1. A radar antenna comprising a spindle, a wave guide mounted on said spindle, and a reflector mounted on said spindle, said reflector being rotatable with respect to said spindle and wave guide on the axis of the spindle.

2. A radar antenna comprising a spindle, a. wave guide mounted on said spindle, a rotatable reflector mounted on said spindle concentric with said wave guide, said reflector being rotatable with respect to said spindle and wave guide on the axis of the spindle.

3. A radar antenna comprising a spindle, a wave guide mounted on said spindle, means for rotating said spindle, and a freely rotatable reflector mounted on said spindle, said reflector being rotatable with respect to said spindle and wave guide on the axis of the spindle.

4. A radar antenna comprising a spindle, a wave guide mounted on said spindle, reversible means for rotating said spindle, and a freely rotatable reflector mounted on said spindle, said reflector being rotatable with respect to said spindle and wave guide on the axis of the spindle.

5. A radar antenna comprising a spindle, a. wave guide mounted on said spindle, reversible means for rotating said spindle, and a freely rotatable reflector mounted on said spindle concentric with said wave guide, said reflector being rotatable with respect to said spindle and wave guide on the axis of the spindle.

OTTO E. SZEKELY.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,479,539 Moseley Aug. 16, 1949 2,543,188 Moseley Feb. 27, 1951 2,544,433 Moseley Mar. 6. 1951 

